/**
2018/7/25
wgg
*/
package main

import (
	"image/color"
	"math/rand"
	"time"
	"os"
	"net/http"
	"log"
	"io"
	"image/gif"
	"image"
	"math"
)

var palette = []color.Color{color.White,color.Black}

const (
	//whiteIndex = 0 //画板中的第一种颜色
	blackIndex = 1 //画板中的下一种颜色
)

func main()  {
	rand.Seed(time.Now().UTC().UnixNano())
	if len(os.Args) > 1 && os.Args[1] == "web" {
		handler := func(w http.ResponseWriter,r *http.Request) {
			lissajous(w)
		}
		http.HandleFunc("/",handler)
		log.Fatal(http.ListenAndServe("localhost:8000",nil))
	}
	lissajous(os.Stdin)
}

func lissajous(out io.Writer){
	const  (
		cycles = 5
		res = 0.001
		size = 100
		nframes = 64
		delay  = 8

	)
	freq := rand.Float64()* 3.0
	anim := gif.GIF{LoopCount:nframes}
	phase := 0.0
	for i := 0; i < nframes; i++{
		rect := image.Rect(0,0,2*size+1,2*size+1)
		img := image.NewPaletted(rect,palette)
		for t := 0.0;t < cycles*2*math.Pi;t += res{
			x := math.Sin(t)
			y := math.Sin(t*freq+phase)
			img.SetColorIndex(size+int(x*size+0.5),size+int(y*size+0.5),blackIndex)
		}
		phase += 0.1
		anim.Delay = append(anim.Delay,delay)
		anim.Image = append(anim.Image,img)
	}
	gif.EncodeAll(out,&anim)
}
